Pollution of water due to pharmaceuticals is an international problem, many compounds in this category are highly refractory resulting conventional wastewater treatment plants are inefficient. Fluoroquinolones (FQs) are one of the classes of broad spectrum antibiotics that are commonly used in both human and veterinary medicine. They inhibit key bacterial enzymes, such as DNA gyrase and topoisomerase IV, that are involved with unwinding the DNA helix for replication and transcription. Ciprofloxacin hydrochloride (CFX), a second generation FQ and one of the most prescribed drugs in the world, and it has been regularly found in wastewater at nanograms levels that could induce bacterial resistance. Ciprofloxacin hydrochloride is a broad spectrum antibiotic that is effective against gram-positive and gram-negative bacteria. It was recommended during the anthrax outbreak in 2001 and has also been used to target biological agents of Legionnaire's disease and typhoid. It also belongs to a class of powerful FQs that have been linked to serious side effects which include ruptured tendons and neurological damage resulting from seizures. The pharmaceutical compounds are often hardly biodegradable, resulting in inefficient removal by conventional wastewater treatment plants (WWTP). Therefore, Ciprofloxacin hydrochloride must be removed to a permissible level from the wastewater before being discharged into drainage system. A number of promising wastewater treatment methods have been used to remove Ciprofloxacin hydrochloride from wastewater such as ozonation, photo Fenton; sonolysis, photolysis and titanium dioxide (TiO2) photocatalytic degradation have been recently applied for the remediation of FQs. Using photocatalyst, an inexpensive and safe semiconductor as photo-oxidant, is an appealing possibility in the perspective of green chemistry, because it is active under natural solar radiation. TiO2 has been extensively employed for the remediation of pollutants. However there are few drawbacks associated with TiO2 including: (i) it has very low surface area (55 m2/g for Degussa P-25 TiO2) and (ii) low porosity and it can be activated only by irradiating with ultraviolet light (wide band gap energies, 3.0 eV for rutile and 3.2 eV for anatase) which is around 4-8% of solar radiation that reaches the earth surface. It is therefore of utmost importance to develop an improved visible active photocatalyst.
Article titled “Photocatalytic study of BiOCl for degradation of organic pollutants under UV irradiation” by F Chen et al. published in Journal of Photochemistry and Photobiology A: Chemistry, Volume 215, Issue 1, 5 Sep. 2010, Pages 76-80 reports Photocatalytic study of BiOCl as BiOCl exhibited high photocatalytic activities for the degradation of rhodamine B, methyl orange and phenol. Surface chloride ions were adverse to the BiOCl photocatalysis and dissociated from BiOCl via reaction with photogenerated holes and electrons under UV irradiation. Conduction band electrons of BiOCl directly reduced either chlorine radical or the azo-bond of MO during the photocatalytic process. Hydroxyl radical was the main oxidative species in the BiOCl photocatalysis, whose generation can be accelerated via enhancing the conduction band electron consumption by MO. After the photocatalytic reaction, the dissolved chloride ion would spontaneously recombine back to the BiOCl photocatalyst, hence qualifies BiOCl as a practical high-activity photocatalyst with long lifetime.
Article titled “Photocatalytic degradation of ciprofloxacin drug in water using ZnO nanoparticles” by M El-Kemary et al. published in Journal of Luminescence, Volume 130, Issue 12, December 2010, Pages 2327-2331 reports the synthesis of nanostructure ZnO semiconductor with ˜2.1 nm diameter using a chemical precipitation method. The resulting nanoparticles were characterized by X-ray diffraction analysis (XRD), Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The optical properties were investigated by UV-vis and fluorescence techniques. The absorption spectra exhibit a sharp absorption edge at ˜334 nm corresponding to band gap of ˜3.7 eV. The fluorescence spectra displayed a near-band-edge ultraviolet excitonic emission at ˜410 nm and a green emission peak at ˜525 nm, due to a transition of a photo-generated electron from the conduction band to a deeply trapped hole. The photocatalytic activity of the prepared ZnO nanoparticles has been investigated for the degradation of ciprofloxacin drug under UV light irradiation in aqueous solutions of different pH values. The results showed that the photocatalytic degradation process is effective at pH 7 and 10, but it is rather slow at pH 4. Higher degradation efficiency (˜50%) of the drug was observed at pH 10 after 60 min. photodegradation of the drug follows a pseudo-first-order kinetics.
Article titled “A Highly Efficient Visible-Light-Activated Photocatalyst Based on Bismuth- and Sulfur-co-doped TiO2” by Y Wang et al. published in J. Phys. Chem. C, 2008, 112 (17), pp 6620-6626 reports titanium dioxide (TiO2) codoped with bismuth (Bi) and sulfur (S) elements was prepared by a simple sol-gel method using tetrabutyl titanate, bismuth nitrate pentahydrate, and thiourea as precursors. The codoped TiO2 calcined at 400° C. exhibits an intense absorption in the range of 500-800 nm. The absorption edge corresponds to a band gap of 2.0 eV. An indigo carmine solution of 20 mg/L was completely photodegraded in 40 min in the presence of such photocatalyst under visible light (λ>410 nm). This highly active photocatalytic performance is associated with the existence of numerous oxygen vacancies, the acidic sites on the surface of TiO2, and the high specific surface area.
Article titled “Degradation of antibiotic ciprofloxacin hydrochloride by photo-fenton oxidation process” by S ShengPeng et al. published in Environmental Engineering Science, 2009, 26 (4), pp. 753-759 reports the feasibility of using a photo-Fenton oxidation process for the degradation of ciprofloxacin hydrochloride. The pH value of solutions, dosages of hydrogen peroxide and ferrous ion, reaction temperature, and the presence of chloride ion, which affect the degradation of ciprofloxacin hydrochloride wastewater, were studied based on the changes of ciprofloxacin hydrochloride concentration and UV-absorbance of the wastewater. Results indicated that ciprofloxacin hydrochloride could be degraded effectively by photo-Fenton oxidation process in a wide pH range of 3.0 to 5.0; the optimum dosages of hydrogen peroxide and ferrous ion were selected as 5.0 and 0.05 mmol L−1, respectively; the increase of reaction temperature had a positive effect, but the presence of chloride ion had an inhibitory one on the degradation of ciprofloxacin hydrochloride. Under optimum conditions of C0=15 mg L−1, [H2O2]=5.0 mmol L−1, [Fe2+]=0.05 mmol L−1, pH 4.0 and 25° C., no ciprofloxacin hydrochloride was detected in the 45-min reaction time. Degradation kinetics of ciprofloxacin hydrochloride by a photo-Fenton oxidation process follows the first-order reaction kinetics model. The photo-Fenton oxidation process was more rapid and effective for the degradation of ciprofloxacin hydrochloride than conventional Fenton process. It is feasible to employ the photo-Fenton oxidation process to treat ciprofloxacin hydrochloride wastewater; the process also provides an effective approach for other antibiotics wastewater treatment.
Article titled “Photocatalytic oxidation of ciprofloxacin under simulated sunlight” by TA Gad-Allah et al. Published in J Hazard Mater., 2011 Feb. 15, 186(1), 751-5 reports photocatalytic degradation of ciprofloxacin using commercial anatase titanium dioxide (TiO2) under simulated sunlight. The rate of reaction was found to be affected by pH, TiO2 concentration and antibiotic concentration. The best reaction rate was obtained in natural ciprofloxacin pH (5.8) and 1000 mg/L TiO2. More titania concentration was found to reduce the reaction rate because of the limitation in light transmittance. From kinetic studies, the reaction was proved to proceed through adsorption step then photooxidation and obeys pseudo-first order kinetics.
Article titled “Microwave-assisted in situ synthesis of reduced graphene oxide-BiVO4 composite photocatalysts and their enhanced photocatalytic performance for the degradation of ciprofloxacin” by Y Yan et al. published in J Hazard Mater., 2013 Apr. 15, 250-251, 106-14 reports a new-type microwave-assisted in situ growth method is developed for the preparation of reduced graphene oxide (RGO)-BiVO4 composite photocatalysts. The as-produced RGO-BiVO4 composite photocatalysts show extremely high enhancement of CIP degradation ratio over the pure BiVO4 photocatalyst under visible light. Specially, the 2 wt % RGO-BiVO4 composite photocatalyst exhibits the highest CIP degradation ratio (68.2%) in 60 min, which is over 3 times than that (22.7%) of the pure BiVO4 particles. The enhancement of photocatalytic activities of RGO-BiVO4 photocatalysts can be attributed to the effective separation of electron-hole pairs rather than the improvement of light absorption.
Chinese patent application no. CN103752332A reports a dried persimmon-shaped visible-light-driven photocatalyst BiOBr and a preparation method thereof. The inventor adopts a low-temperature solvothermal method, controls the morphology of a halogen-bismuth-oxide visible-light-driven photocatalyst by controlling the dosage of a bismuth source and a bromine source and adding a structure guiding agent, and successfully prepares the novel efficient visible-light-driven photocatalyst BiOBr with novel and special morphology, the dried persimmon shape. The visible-light-driven photocatalyst disclosed by the invention has good visible-light catalytic activity, can completely degrade a plurality of organic pollutants (such as methylthionine chloride and methyl orange) within a short period of time under irradiation of visible light, is small in light corrosivity, good in reusability and large in market potential, can be applied to industrial production, and especially has good application value in photocatalytic decomposition of organic pollutants by solar energy.
Therefore, there is need in the art to develop a cost effective, recyclable, pollution free and environmentally friendly process for photocatalytic degradation (PCD) of pharmaceutical drugs including, for example, ciprofloxacin hydrochloride (CFX), naproxen or dyes including, for example, orange dye by using visible active photocatalyst. Accordingly, the present disclosure is directed to novel BiOS, BiOP as visible active photocatalysts, which have been shown to be effective for photocatalytic remediation of pharmaceutical pollutants, particularly ciprofloxacin hydrochloride and Naproxen and dye such as orange dye from wastewater using artificial radiation or solar radiation.